Dehydrogenation and isomerization of olefins



Patented May 7, 1946 TENT oFFicr:

: namaooam'rion AND isoiuamz'svrron or own-ms 'Wilson D.- Seyi'ried,'Wooster, and H. Has- 88, Baytown, Tex., assignors to Standard 011'Development Company, a corporation of Delaware Application July 21,1944, Serial No. 545,898

The present invention is directed to ment of a hydrocarbon mixtureincluding oleiins and paraflin's. In its more specific aspects, thepresent invention is directed to a process for treating hydrocarbonincluding the treatment of a 'mixtureincluding oleflns' andparaflins ina thermal catalytic step and the subs quent; treatment oi at least aportion of the product from the thermal. catalytic step bya solventextraction step to obtain a fraction with a high olefin concentrat on. t

It is conventional to the art tosubiect a hydrocarbon mixture having ahigh concentration 01 mono-oleilns to a thermaLcatalytic step whereinthe mixture is contacted with catalyst under conditions to causeasubstantial portion of the mono-olefin to be converted to diolefin. The

the treattion zone.

In accordance with the present invention a mixture of C4 hydrocarbon-sincluding parafiin and mono-oleiins is treated in a thermal catalyticzone with a catalyst capable of converting substantial amounts of C4mono-oleflns to butadiene and I capable as well or isomerizingsubstantial amounts of the C4 -mono-o1efln.- vThe product from thiscatalytic zone is treatedto separate butadiene therefrom and theremainder i redioleiln is removed from the product, leaving a residueincluding mono-oleflns and p'araflins. It

is conventional to recycle a portion of the residue to thedehydrogenation step, but in order to prevent the building up of anundesirably high concentration oi. parafllns. in the dehydrogenationzone it has heretofore been necessary to discard a portion 01' theresidue, which contains valuable I amounts of olefins as well as theundesired paraihns We have now discovered that by theuse of a suitablecatalytic mass with which the hydro carbon mixture is broushtin contactin the thermal treatment step, substantial isomerization of mono-olefin;is obtained as well as conversion.

of mono-olefin to dioleiin., The employment of this catalyst in thethermal catalytic step enablesthe production or a product from which thediclefln may be removed to produce a residue read:

ily separable into mono-oleflns and parailins whereby the mono-olelinsmay be recycled to the thermal catalytic zone without the necessity oidiscarding any of these valuable materials from the system The inventionhas been found particularly desirable in the treatment of a mixture ofC4 hydrocarbons including paraflins and o'leilns. It is common incommercial operations to prepare a C4 fraction by distillation. and sucha fraction will contain a mixture or butylene-l, butylene-z,

removed from the product of the thermal cataf lyticzone the remaindermay be subjected to any one of several alternative treatments. Ifdesired, a portion oi the remainder may be returned directly to thedehydrogenation zone and the remaining portion subjected to anextractive distillation step for the removal 01 paraflins and theconcentration of mono-oleflns, and the concentrated mono-olefin fractionthen returned to the feed and the admixture sent to the extractivedistillation step for removal or paramnic hydrocarbons and then to thedehydrogenation zone. I

As an alternative," but usually less desirable, procedure. the remaindermay be sent to the ex-' tractive distillation step for the removal of,paraflins and then mixed with the feed and sent to y the catalyticdehydrogenation step.

normal butane and isobutane. Such a mixture is not considered adesirable reed ior a catalytic 'dehydrogenationfiep in the production of-dioieiins because the constituents other than butylene-l andbutylene-fl serve principally as diluents As has been stated heretofore.the composition of the catalyst mass employed in the thermaldehydrogenation step is of critical importance. It has been founddesirableto employ for this catalytic mass'a material having thefollowing composition:

Per cent M 80 rotor 14 Rio 3 CuO- 8 when. present in the reaction zone.If this mixture of mono-cleans and parailin; is subjected to extractivedistillation, the butylene-2 may be as It will be noted that thecatalyst compositim acetone or furfural as the solvent.

oxide shown as F8203, may be F8304, FeO, or

mixtures thereof. This likewise holds true for the other oxides of thecatalyst composition. When this catalytic mass is employed in a thermalzone at a temperature in the range of 1150 to 1300 F. it is capable ofproducing a product comprising diolefin. and having the ratio ofmono-oleflns therein of 1.67 parts of butylene-2 to 1 part ofbutylene-l. It is desirable to employ from 5 to volumes of steam pervolume of hydrocarbon in the catalytic zone and a pressure ranging fromatmospheric to 10 pounds per square inch above atmospheric, with spacevelocities ranging from 200 to- 500 volumes of feed per volume ofcatalytic mass .per hour.

A preferred embodiment of the present invention will now be described inconjunction with the drawing, in which the sole figure is in the form ofa diagrammatic flow sheet.

In the drawing, A designates a vessel for carrying out an extractivedistillation step, and B an apparatus for conducting a catalyticdehydrogenation step. An inlet line H, controlled by valve l2,discharges into an upper portion of vessel A and serves to supply amixture of C4 hydrocarbons including mono-oleflns and paraflins as feedto the extractive distillation step. Solvent is added to vessel A bymeans of line It, discharging into the upper portion of vessel A at apoint above the entrance of line' ll thereto. A number of organicsolvents are available which are capable of separating parafiins fromolefins -in the extractive distillation step, and of these with a minorportion of parafiins is treated in a thermal catalytic zone whichcontains a dehydrogenation catalyst consisting approximately of 80% MgO,14% FezOa, 3% K20 and 3% CuO maintained at temperatures ranging from1150" to"1300 F. This thermal catalytic zone causes the conversion ofsubstantial portions of butylenes to butadiene and the isomerization ofthe remaining butylenes so that the butylenes in the. product removedfrom this zone havea ratio of butylene-2 to butylene-l of about 1.67to 1. The product removed from the catalytic thermal zone is quenchedrapidly, preferably by being contacted first with a water spray in thereactor, then by heat exchange, then with an oil quench step, then withadditional heat exchange, and finally with a water quench step. Thesequenching steps are well known to the dehydrogenation art andaccordingly are not shown in detail in the v drawing. After the producthas been quenched it may be treated by distillation to separate C3bydrocarbons therefrom and C5 and heavier hydrocarbons therefrom. Theremoval of the Ca and C5 hydrocarbons is usually accomplished bydistillation equipment operated in connection with the dehydrogenationunit and is indicated diagrammatically in the drawing by the outlet line25 for the removal of C3 hydrocarbons from zone B and outlet line 26 forthe removal of C5 and heavier hydrocarbons fromthis zone. The C4 streamfrom unit B may then be sent through line known solvents it is preferredto employ either When employing acetone as the solvent, the solvent isdischarged into tower A via line l3. A solution of .solvent andmono-olefins with 9. minor portion of paraifin is removed from the lowerportion of tower A through line l4 and discharged into stripping towerii. In the strippingtower a hydrocarbon fraction comprising a majorportion of mono-olefin and a minor portion of parafiin is discharged asoverhead through line It and is sent as feed to the thermal catalyticdehydrogenation step 13.

The overhead from tower' A consists of solvent and paraflinichydrocarbons. This overhead fraction is removed through line |'I to thelower portion of a tower l8, where the vapors are washed by beingcontacted with a stream of water discharged into the upper portion oftower I8 through line H. The washed parafiinic vapors are removed asoverhead through outlet 20. The washing water having solvent dissolvedtherein is removed from the bottom of tower i8 by line 2| and is sent todistillation tower 22 in order to separate the solvent from the water.Concentrated solvent is removed from tower 22 as overhead by line it,and water is removed through line l9and returned to tower l8.

Mono-olefins are removed as overhead from stripping vessel li'and offthrough line l8, while solvent is recovered as bottoms and removedthrough line 24. The solvent in line 24 is ad- 21 to abutadiene removalstep in unit 28. It is usual to remove butadiene from a mixture of C4hydrocarbons by solvent extraction, and since this is conventional theseveral manipulative operations are not shown in detail in the drawing,but the butadiene is simply indicated as being removed from unit 28 bymeans of outlet line 29 and the residue hydrocarbons, comprisingprincipally butylene, are removed through line 30.

The stream removed from vessel 28 by means of line 30 usually comprisesbutylene-l, butylene-l, butylene-2 and small amounts of isobutylene,isobutane and normal butane, which act as impurities in the stream. Inthe preferred operation the stream flowing in line 30 is split, with aportion being withdrawn through line 3| and admixed with the streamflowing in line l6 and returned to the catalytic. dehydrogenation stepconducted in vessel B, while the remainder is tion flowing in line ,30will usually be contain inated by a small portion of high boiling pointpolymers, and accordingly it is desirable to pass the stream from line30 into distillation tower 32.

where thepolymer is separated as bottoms and removed through outlet 33,while the C4 hydrocarbons are removed as overhead through line 24 andare passed through inlet line to extractive distillation tower A.

It will be understood that, if desired, valve 2| may be closed in orderto send all of the .C4 fraction removed from unit 28 to the extractivedistillation step; It will also be evident that, if desired, therecycled fraction may; be extracted either continuously or in astep-wise manner;

that is to say, all of the material in line 30 may be returned directlyto vessel B until the impurities in the stream have built up to apredetermined value and then all of the stream containing theseimpurities may be sent to extractive,

CuO and is maintained at a temperature in the range of 1150 to 13001".to cause the isomerization of substantial amounts of C4 mono-olefin andthe formation of substantial amounts of C4 dioleiin in the product,removing product from the catalyst and separating dioleiin therefrom;

2. A method in accordance with claim 1 in which the product removed fromthe catalyst follow this procedure, the C4 hydrocarbon irac- P tionemployed as feed may be supplied to the system through inlet line 35,controlled by valve 36, when the hydrocarbon feed mixture is supplieddirectly to the catalytic dehydrogenation step in unit B, substantialportions of the butyienes in the feed are converted to butadiene and thebutylenes are isomerized so that the product removed from vessel B has aratio of butyiene-2 to butylene-i of 1.67 to 1, and after the removalhas dioleiin and paraiiin removed therefrom andin which the remainingunsaturated constituents are again brought into contact with thecatalyst.

3. A method in accordance with claim 1 inwhich the major portion of theC4 mono-olefin in the feed is butylene-l.

of butadiene from the product in unit '28 the remainder may be readilyseparated into a paraflin fraction and an olefin fraction in theextractive distillation step in vessel A. This alter native procedurewill usually not be desirable because the hydrocarbon feed will usuallycontain substantial amounts of paraiiln which. will be thermally treatedwith'the oleflns in the catalytic dehydrogenation zone B, and which, forthe most part. will pass through the zone without change, but will serveas a diluent in the zone. In order to use the several portions of theapparatus in an optimum manner,.it is usually desirable to send a streamhaving oleilns concentrated therein tothe dehydrogenation zone, and toobtain such a stream it is desirable to subject the feed stream to apreliminary extractive distillation step to remove at least a portion ofthe parafilns therefrom.

It will be seen that we have disclosed a method for treating. a C4hydrocarbon stream comprising paraflins and mono-olefins to isomerizebutylenes therein, with the subsequent separation of paramnic materialsfrom the butylenes b'y extraction. It will also be seen that in additionto the treatment of a mixture comprising paraflins and butylenes inorder to separate parafllns from the stream without discarding valuablebutyle'nes therefrom, we also convert appreciable portions ofmonov-oleflns to diolefins.

While the present invention has been described and illustrated withrespect to the isomerization of butylene-l to butylene-B, it is alsopossible in the present-invention to isomeriae butyiene-2 to butylene-l.In an operation where 100 I parts of butylene-2 were charged to thedehydrogenation step B at the conditions encompassed in the presentinvention, there were produced 30 parts of butylene-l, 17.5 parts ofbutadiene, 2.5 parts of other hydrocarbons, with 50 parts of thebutylene-2 passing unchanged through the vessel 8. v

Having fully described and illustrated the practilce in?! the presentinvention. what we desireto C 8. i

4, A method in accordancewith claim 1 in which at least a major portionof the C4 monoolefin is butylene-Z.

' 5. 'A method for treating hydrocarbons comprising the steps ofsubjecting a feed inciuding' C4 parafiin and C4 mono-olefin to anextraction step to remove paramn from the feed, removin product from theextraction step and bringing it into contact with a catalyst whichcomprises approximately MgOz, 14% FezOa, 3% K20 and 3% CuO and ismaintained at a temperature in the range of 1150 to 1300 F., maintainingthe hydrocarbons in contact with the catalyst for a suiiicient intervalof time to allow the formation of substantial amounts of C4 dioleiin andthe isomerization of substantial amounts of C4 monoolefln, removing theresulting hydrocarbons from contact with the catalyst, separatingdiolefln therefrom and employing at least a portion of the remainder asfeed for the extraction step.

6. A method in accordance with claim 5 .in which at least a majorportion of the C4 monoolefln in the feed is butylene-l. 7

7. A method in accordance with claim 5 in which at least a major portionof the C4 monoolefin in the feed is-butylene-2.

8. A method for treating hydrocarbons comstock from the extraction step,separating solvent therefrom and subsequently contacting it with avcatalyst which comprises approximately 80% M80. 14% R201. 3% K20 and 3%CuO in a catalytic reactor zonemaintained at a temperature in the rangeof 1150 to 1300 F., maintaining the hydrocarbon mixture in the catalyticzone for a sumcient interval of time to cause the formation ofsubstantial amounts of butadiene and I butyiene-ii, removing productfrom the catalytic zone. separating butadiene from the product,

separating the remainder of the product into a first portion and asecond portion, returning the ilrstportion to the catalytic zone andreturning- I "the second portion to the extraction step.

1. a method for treating a hydrocarbon naetion including a C4paraflinand a C4 mono-olefin comprising the steps of bringing the fraction intocontact with a catalyst which comprises approxi-- mately s07, MgO, 14%F0203, 3% K20 and 3% 9. A method in accordance with claim a in Y whichthehydrocarbon sent tothe catalytic zone is diluted with steam in aratio of '1 parts of steam to 1 partlof hydrocarbon. in which thecatalytic zone is maintained at a pressure in the range of atmosphericto 10 pounds per square inchabove atmospheric. 4 WILSON D. m. SAM H.KAS'll'lNGB.

